Ported unloader sleeve

ABSTRACT

A compressor for compressing gases from a source having at least one piston and cylinder, exhaust ports and valves, and a suction port and valve therefor, together with at least one auxiliary port in the cylinder wall, which, when uncovered by the piston during a portion of the stroke of the piston, allows additional gases to be drawn into the cylinder from the source therethrough, and a ported unloader sleeve which provides means for holding open the suction valve when moved to an unloading position and permits normal operation of the suction valve when moved to a loading position wherein the cylinder may possess the advantages of both an auxiliary port and an unloader sleeve in the same apparatus.

United States Patent Grant et al.

[ Oct. 28, 1975 PORTED UNLOADER SLEEVE 3,490,683 l/l970 Kocher 417/298 [75] Inventors: Hendrie J. Grant, St. Paul;

Lawrence J. Shirek, Minneapolis, Primary Exammer Ailan Cohan both of Minn. Attorney, Agent, or Firm-C. F. Renz [73] Assignee: Westinghouse Electric Corporation, [57] ABSTRACT Plttsburgh, A compressor for compressing gases from a source [22] Fil d; N 22, 1974 having at least one piston and cylinder, exhaust ports and valves, and a suction port and valve therefor, to- [21] Appl' 526,291 gether with at least one auxiliary port in the cylinder wall, which, when uncovered by the piston during a 52 US. Cl. 417/490; 417/503 Portion of the Stroke of the Piston, allows additional 51 Int. 01. F04B 7/04 gases to be drawn into the Cylinder from the source [58] Field of Search 417/490, 493, 503, 29s, therethreugh, and a ported unloader Sleeve which p 417/297 vides means for holding open the suction valve when moved to an unloading position and permits normal [56] References Cited operation of the suction valve when moved to a load- UNITED STATES PATENTS ing position wherein the cylinder may possess the advantages of both an auxiliary port and an unloader 417/493 Sleeve in the Same apparatus 2,626,099 l/1953 Ashley 417/298 6 Claims, 4 Drawing Figures [8 l7 l6 l6 l L 7 3| n 4 Q 0! in Q 510 s 1H: "-1 4| 43 a 43 42 H Q 42 FIG. I.

FIG. 2.

Sheet 1 of 2 U8. Patent '00:. 28; 1975 U.S. Patent Oct.28, 1975 Sheet20f2 3,915,597

PORTED UNLOADER SLEEVE BACKGROUND OF THE INVENTION This invention generally relates to underloader mechanisms for multi-cylinder compressors used in refrigeration systems, air compressors, and various other compressing apparatus utilizing unloading mechanisms. More specifically, this invention discloses a high efficiency compressor having an auxiliary port in the cylinder wall for intaking additional gas from the source together with a ported unloaded sleeve surrounding the cylinder for selectively unloading the cylinders.

In refrigeration systems utilizing the expansion of compressed gases as a means of heat transfer wherein the demand for compressed gas varies according to the conditions existing in the refrigeration device, it is desirable to change the capacity of the compressor without periodically shutting down the compressor device or varying the speed of the motor which drives the compressor. In a multi-cylinder compressor, this is normally done by unloading one or more of the cylinders. The unloading of the individual cylinders is usually accomplished by an unloading sleeve surrounding the cylinder which, when moved to an unloading position, holds open the suction valves of that cylinder so that the gas is not compressed during the compression cycle of the piston. By this method, the capacity of the compressor may be reduced to match the demand of the refrigeration device thereby permitting continuing operation of the motor which drives the compressor device without sacrificing efficiency in compressor operation.

It is also desirable to use a type of compressor or cylinder design which permits an increased volumetric efficiency. One means of accomplishing this desired fea ture is to provide an auxiliary port in the cylinder wall. If this auxiliary port is disposed on the cylinder wall in a position where it is uncovered by the piston during a portion of the suction stroke, additional gas may be drawn into the cylinder, without restriction, as would be the case when gas enters the cylinder through the suction valves, since the suction valves have limited cross-sectional area and are held closed by spring means.

The advantages inherent in the use of a sleeve surrounding the cylinder for unloading means, instead of other types of unloading mechanisms such as shown by U.S. Pat. No. 2,185,473 issued to Neeson, are its amenability to simple servo drive means and its greater mechanical tractability for activating the unloader mechanism. When a sleeve is utilized for unloading the cylinder, the unloading sleeve drive means need only engage the sleeve at one peripheral point as the large bearing surface between the unloading sleeve and the cylinder sleeve permits the desired tractableness for holding open the suction valves of the cylinder.

PRIOR ART Although U.S. Pat. No. 2,185,473 discloses a compressor with unloading means and a ported cylinder sleeve, there are no prior patents known by applicants to disclose the combination of a ported cylinder sleeve also having an unloader sleeve surrounding the cylinder in an arrangement as provided by the subject invention summarized hereinbelow.

SUMMARY OF THE INVENTION It is an object of the present invention to retain the use of a sleeve for unloading the cylinder when the cylinder is provided with auxiliary ports. The combination of those desired features is accomplished by a novel arrangement of the ports in the unloader sleeve with structural means to ensure substantial alignment between the cylinder ports and sleeve ports when the sleeve is moved to various positions. In this manner, the unloader sleeve surrounding the cylinder may be used to unload the cylinder while at the same time, not restricting the flow of additional gas from the source into the cylinder when an auxiliary port is provided in the cylinder wall for increased volumetric efficiency. Thus, according to this invention, the advantages of two desirable features for a multi-cylinder compressor are achieved.

In operation, the unloader sleeve may be moved to either one of two positions; a loading position and an unloading position. In the loading position, the unloader sleeve is in a position whereby the suction valves are permitted to function normally, that is, opened during the suction stroke of the piston due to either a rela tively low pressure within the chamber during the expansion stroke of the piston or by other means, and closed during the compression stroke of the piston. Additionally, since an auxiliary port is provided in the cylinder wall and a port in substantial alignment therewith, is provided in the unloader sleeve, additional gas is drawn from the source into the cylinder, without restriction, during the terminal portion of the suction stroke of the piston. In this manner, the compressor cylinder is permitted to operate with increased volumetric efficiency due to the provision of additional ports through which the chamber may freely communicate with the source of gas to be compressed.

Should it be necessary to reduce the output of the compressor, any one of the several cylinders may be unloaded. Associated with each cylinder is a means to selectively move the unloader sleeve to an unloading position. Usually, a hydraulic cylinder is provided to control the position of the unloader sleeve in response to a condition elsewhere in the system. When the unloader sleeve is moved to an unloading position, the suction valves associated with the cylinder are held open by a mechanism associated with the unloader sleeve. Consequently, the cylinder is unloaded as gas may enter into and be exhausted from the cylinder through the suction valve port without substantial compression thereby reducing the load of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a sectional view of the housing, cylinder, and piston, during an intermediate portion of suction cycle under loading conditions.

FIG. 2 shows a sectional view of the housing, cylinder, and piston, during the terminal portion of the suction cycle under loading conditions.

FIG. 3 shows a section view of the housing, cylinder, and piston, during the compression cycle under loading conditions.

FIG. 4 shows a sectional view of the housing, cylinder, and piston, during the unload condition of the cylinder.

DETAILED DESCRIPTION OF THE INVENTION In a multi-cylinder compressor apparatus having unloading means, each cylinder may be equipped with an unloader mechanism. Since the unloading mechanisms are substantially identical for each cylinder, the description and operation of only one cylinder will be described herein. An explanation of the operation of the invention is described during the compression and expansion cycles while under load and unload conditions.

Referring to FIG. 1, housing 10, cylinder wall 20, and piston 30 are shown during an intermediate portion of the expansion cycle when the unloader mechanism is not activated. Gas is drawn into compression chamber 31 from chamber 11 and is discharged through annular discharge port 19 into chamber 17. Should this invention be used in a refrigeration system, chamber 11 would contain gas from an evaporator (not shown) and chamber 17 would supply a condenser coil (not shown). However, it is understood that this invention may be utilized with any type of compressor apparatus. During the suction stroke piston 30 moves in the cylinder 20 to increase the volume of the compressor chamber 31 thereby allowing gases from chamber 11 to be drawn through annular intake port 12. Port 12 has a ring type suction valve 13 which is held closely by spring 14 and is caused to open in response to a relatively low pressure in chamber 31 relative to chamber 11, to allow gas to be drawn into the compression chamber 31. Piston 30 is moved by a connecting rod (not shown) and drive means (not shown).

During the terminal portion of the suction stroke, as illustrated in FIG. 2, auxiliary port 43, which may be a series of peripherally located ports in cylinder wall 20, is uncovered by piston 30 to allow additional gas to be drawn into the compression chamber 31 from chamber 11. According to the invention, a port 41, which also may be a series of peripherally located ports, is provided in unloader sleeve 40 in substantial alignment with auxiliary port or ports 43 to permit the use of an unloader sleeve around the cylinder. An annular recess 42 is provided in the unloader sleeve 40 interconnecting the radially spaced ports 43 to facilitate alignment between auxiliary port or ports 43 and the port or ports 41 in the unloader sleeve. The provision of the auxiliary port and the port in the sleeve ensures increased volumetric efficiency in operation of the compressor cylinder. By the addition of auxiliary port 43 and port 41, an unrestricted flow of gas is allowed to flow into the chamber 31 when the auxiliary port is uncovered by pis'ton30. Consequently, the volumetric efficiency of the cylinder is substantially increased and thus, this desired feature of a compressor may be retained, even with the use of an unloader sleeve surrounding the cylinder. Recess 42 also provides a trap for the lubricating oil within the compressor apparatus so that any excess oil accumulating in the space as provided by recess 42 may be drained back into gas source 1 1 and from there to the oil reservoir (not shown) through oil drain passage 44.

FIG. 3 shows the cylinder during the compression cycle. The gas in compression chamber 31 is compressed by piston 30 until a predetermined high pressure is reached, thereby forcing open the ring type exhaust valve 15 which is otherwise held closed by spring 16 and allowing the compressed gas to discharge through port 19 into chamber 17. Suction valve 13 is held closed by the high pressure in chamber 31 during the compression cycle to prevent the flow of fluid back into chamber 11. Suction valve 13 may also be held closed by spring 14.

FIG. 4 shows the cylinder during an unload condition. In this condition, unloader sleeve 40 is moved to an unload position by hydraulic cylinder 50, engaging the unloader sleeve 40 by member 51. Pin 45, which is connected to unloader sleeve 40, engages suction valve 13 so that the valve may be held open during the expansion and compression cycles of the piston. In practice, several pins such as the pin 41 are disposed around cylinder 20 between unloader sleeve 40 and the ring type suction valve 13. During the unload condition, the pins contact the underside of the suction valve 13 as shown by FIG. 4 to maintain the suction valve in the open position so that gas may enter the compression chamber 31 from chamber 11 through passage 12 during the suction stroke, and exhaust from compression chamber 31 through passage 12 into chamber 11 during the compression cycle without substantial compression, thereby unloading the cylinder. In this manner, the pressure in the compression chamber does not build up to force open exhaust valve 15 thus preventing any discharge of compressed gas from compression chamber 13 into chamber 17. Consequently, in a multi-cylinder compressor, only those cylinders which are loaded may operate to supply compressed fluid to the utilization device (not shown).

The invention as previously described, discloses an unloader mechanism for a cylinder having an auxiliary port, which is not known by the applicants to exist in the prior art. The essence of the invention is the provision of a port in the unloader sleeve so that a sleeve may be utilized with a cylinder having an auxiliary port in the cylinder for increased volumetric efficiency.

Even though springs are shown to hold closed the suction valves and the discharge valves, it is not the intention of the applicants to limit the invention to a cylinder of that type having a valve structure as shown. For instance, instead of using a ring valve for the suction ports and the exhaust ports, several discrete valves could be used for the several ports. Additionally, cams and push rods may be used to open and close the suction and discharge valves. Other types of means to hold close those valves may also be used. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation as shown and described herein, and accordingly, all suitable modifications and equivalents may be resorted to, as falling within the scope of the invention as claimed.

We claim:

1. In combination with a compressor for compressing gases from a gas source having at least one cylinder and movable piston defining a compressor chamber therewith together with a discharge port having valve means for discharging compressed gases and an inlet port having suction valve means which is open during the expansion stroke of the piston and at least one auxiliary inlet port in the cylinder wall for intaking additional gas from said source when uncovered during a portion of the stroke of said piston; an unloader mechanism for selectively unloading the cylinder comprising; a movable sleeve surrounding said cylinder and having a port in substantial alignment with said'auxiliary port and said source of gas to be compressed, means operated by movement of said sleeve to hold open said suction valve means when said sleeve is moved to an unloading position and to permit normal operation of said suction valve means when said sleeve is moved to a loading position, and means to selectively move said unloader sleeve between the loading and unloading positions whereby the cylinder of the compressor may simultaneously utilize an unloader sleeve for unloading the compressor and an auxiliary port for increased volumetric efficiency.

2. The invention as defined in claim 1 wherein the suction valve means is an annular shaped valve which is held closed by spring means and is open during the expansion stroke of said piston.

3. The invention as defined in claim 2 wherein the means operated by movement of the unloader sleeve comprises at least one pin connected to said sleeve and disposed around said cylinder between said sleeve and said valve to hold open said valve when said sleeve is moved to an unloading position; and permit normal operation of said valve when said sleeve is moved to an unloading position.

4. The invention of claim 1 wherein a recess is provided in the unloader sleeve between said auxiliary port and sleeve port to facilitate alignment said auxiliary port and said port in said sleeve.

5. The invention of claim 1 wherein the means to selectively move said unloader sleeve between the loading and unloading positions comprises hydraulic means.

6. The invention of claim 4 in which an oil drain passage is provided between said recess and said gas source. 

1. In combination with a compressor for compressing gases from a gas source having at least one cylinder and movable piston defining a compressor chamber therewith together with a discharge port having valve means for discharging compressed gases and an inlet port having suction valve means which is open during the expansion stroke of the piston and at least one auxiliary inlet port in the cylinder wall for intaking additional gas from said source when uncovered during a portion of the stroke of said piston; an unloader mechanism for selectively unloading the cylinder comprising; a movable sleeve surrounding said cylinder and having a port in substantial alignment with said auxiliary port and said source of gas to be compressed, means operated by movement of said sleeve to hold open said suction valve means when said sleeve is moved to an unloading position and to permit normal operation of said suction valve means when said sleeve is moved to a loading position, and means to selectively move said unloader sleeve between the loading and unloading positions whereby the cylinder of the compressor may simultaneously utilize an unloader sleeve for unloading the compressor and an auxiliary port for increased volumetric efficiency.
 2. The invention as defined in claim 1 wherein the suction valve means is an annular shaped valve which is held closed by spring means and is open during the expansion stroke of said piston.
 3. The invention as defined in claim 2 wherein the means operated by movement of the unloader sleeve comprises at least one pin connected to said sleeve and disposed around said cylinder between said sleeve and said valve to hold open said valve when said sleeve is moved to an unloading position and permit normal operation of said valve when said sleeve is moved to an unloading position.
 4. The invention of claim 1 wherein a recess is provided in the unloader sleeve between said auxiliary port and sleeve port to facilitate alignment said auxiliary port and said port in said sleeve.
 5. The invention of claim 1 wherein the means to selectively move said unloader sleeve between the loading and unloading positions comprises hydraulic means.
 6. The invention of claim 4 iN which an oil drain passage is provided between said recess and said gas source. 